Conventionally, “HFC refrigerants” such as non-flammable R410A have been used as a refrigerant for a refrigeration cycle performed by an air-conditioning apparatus. Unlike conventional “HCFC refrigerants” such as R22, R410A has an ozone depletion potential (hereinafter referred to as “ODP”) of zero and does not damage the ozone layer. However, R410A has the property of a high global warming potential (hereinafter referred to as “GWP”).
Therefore, as part of prevention of global warming, studies are underway to shift from HFC refrigerants with a high GWP such as R410A to refrigerants with a low GWP.
Candidates for such a low-GWP refrigerant include HC refrigerants such as natural refrigerants R290 (C3H8; propane) and R1270 (C3H6; propylene). However, unlike non-flammable R410A, these refrigerants are highly flammable, and therefore attention needs to be paid to refrigerant leakage.
Candidates for such a low-GWP refrigerant also include HFC refrigerants that do not have a carbon double bond in their composition, such as R32 (CH2F2; difluoromethane) with a lower GWP than R410A, for example.
Candidates for such a refrigerant also include halogenated hydrocarbons that are a type of HFC refrigerant, similar to R32, and that have a carbon double bond in their composition. Examples of such halogenated hydrocarbons include HFO-1234yf (CF3CF═CH2; tetrafluoropropene) and HFO-1234ze (CF3—CH═CHF). Note that, to be distinguished from HFC refrigerants, such as R32, not having a carbon double bond in their composition, HFC refrigerants having a carbon double bond are often referred to as “HFO” using “O” in olefin (unsaturated hydrocarbons having a carbon double bond are called olefins).
These low-GWP HFC refrigerants (including HFO refrigerants) are not as highly flammable as HC refrigerants such as the natural refrigerant R290 (C3H8; propane), but are slightly flammable, unlike the non-flammable R410A. Therefore, as in the case of R290, attention needs to be paid to refrigerant leakage. Hereinafter, refrigerants that are flammable, including even those slightly flammable, are referred to as “flammable refrigerants”.
In the case where a flammable refrigerant leaks into the indoor living space, the refrigerant concentration in the room increases and may reach a flammable concentration while the operation is stopped (while an indoor fan is not rotating). That is, a flammable concentration is not developed by slow leakage in cases such as when a pinhole is formed in a heat exchanger and when a flare joint is loose, because the leakage speed is low. However, a flammable concentration is likely to be developed by rapid leakage in cases such as when a connection portion between pipes is broken by an external force and when a flare joint comes off, because the leakage speed is high. Note that while the air-conditioning apparatus is in operation, even if the refrigerant leaks, the refrigerant concentration does not increase to a flammable concentration, because the indoor air is agitated and the leaked refrigerant is diffused.
In view of the above, there is disclosed a split type air-conditioning apparatus that includes a temperature sensor disposed at a position in a refrigerant circuit where liquid refrigerant is likely to accumulate, more specifically, at the lower part of a header of an indoor heat exchanger, and a refrigerant leakage determining unit, which determines that the refrigerant is leaking when the refrigerant temperature detected by the temperature sensor decreases at a speed higher than a predetermined speed while a compressor is stopped (see, for example, Patent Literature 1).